diff --git a/sys/src/cmd/ip/ipconfig/main.c b/sys/src/cmd/ip/ipconfig/main.c
index 6d61db431..bbd718ca4 100644
--- a/sys/src/cmd/ip/ipconfig/main.c
+++ b/sys/src/cmd/ip/ipconfig/main.c
@@ -1233,6 +1233,8 @@ dhcprecv(void)
 		if(!validip(conf.mask) || !Oflag){
 			if(!optgetaddr(bp->optdata, OBmask, conf.mask))
 				ipmove(conf.mask, IPnoaddr);
+			if(ipcmp(conf.mask, IPv4bcast) == 0)
+				ipmove(conf.mask, IPnoaddr);
 		}
 		DEBUG("ipaddr=%I ipmask=%M ", conf.laddr, conf.mask);